Slip-on and cat removal on FI bike

**Paulus** · 21st November 2007, 15:36

What is the general opinion from you tuning gurus as to replacing a standard silencer with a slip-on and removing the cat? Is this usually enough of a change to require a Power Commander or is that normally only needed for more extensive mods (I realise this is a bit like asking how long is a piece of string)? Bikes are an 04 ZX-10R and an 06 R1.

**vifferman** · 21st November 2007, 16:13

Weeeellllll......
It depends on how rich the bike was running before the zorst changes, and how much difference the slip-on/cat removal makes.
F'rexample, the VFR has a Satantune and a Unfilter, and runs OK-ish (i.e., not worse) with no Power Commander. The PC is mainly improving things that are crap anyway on a totally stock bike, and allowing for the fact I've disabled the O2 sensors, so the ECU isn't taking care of the low rev / small throttle opening stuff any more. Apparently, replacing the headers and cat on the 2000/2001 VFRs with those from the 1998/1999 VFR (larger diameter, no cat) doesn't make a huge difference, even with an aftermarket zorst. This may be down to a fairly mild state of tune compared to the R1 or ZX10R, so it doesn't necessarily translate.

If you're asking whether you should risk removing the cat and OEM exhaust when you don't intend to fit a PC, then I'd say to not bother about the cat, and that the aftermarket muffler won't make the bike run badly. I'm also of the opinion that anything short of a full race system doesn't make a huge difference to fueling.

But then again, I'm just plucking all this outta my butt, so my advice is worth what you paid for it.

**NinjaBoy** · 21st November 2007, 17:01

Haven't had experience in the bikes you're talking about but have recently fitted a full exhaust system to an 06 GSXR600. This removed a fairly large and heavy cat but the headers were very similar in size and a lot lighter. This is my race/track bike which initially had no PC.

Found this setup very difficult to get smooth crisp throttle response and a general lack of pep vs my road bike , 07 ZX6R.

I fitted a PC loaded with a mate's custom map with a very similar setup. He had a slip-on not full exhaust. Instantly I got all the things that the standard ZX had.... crisp and smooth throttle response and noticeable difference in power and speed.

However, my mate was still able to burn me down the back straight of Taupo. So its booked in for a Dyno session in couple of weeks. See what happens then.

**imdying** · 22nd November 2007, 12:52

You should get the PCIII cause they set the fuel curve up all munted to avoid emissions testing targets, not cause of the muffler change

**vifferman** · 22nd November 2007, 13:12

Originally Posted by imdying

You should get the PCIII cause they set the fuel curve up all munted to avoid emissions testing targets, not cause of the muffler change

True, and that's what I was getting at. Typically, the fueling is way too lean at the revs they do the testing at, but can be a bit rich everywhere else. AFAIK, because they can't set every bike up with ideal fueling for that particular bike, the mapping is on the rich side. This may be so that guys in Mrka can't sue the bike manufacturer because it ended up WAAAAY too lean when they put a K&N and Two Bros on it and cooked the engine.

Actually, I just disconnected the PC this morning, as I couldn't get the mapping right - it's OK over most of the range, but not at low revs or when cruising. Some time I must book a dyno session.

**Gremlin** · 24th November 2007, 00:29

re the 10, the slip on and cat isn't a big difference really, from stock. Just depends why you are removing it, do you want to gain, or just make it sound better etc. Generally, on the 10, you just disable the cat, rather than remove, as the kawasaki bastards made it part of the headers. At least the cat motor doesn't have a load sensor like the gixxer.... now THAT really does you!

If you're wanting to gain power, improve delivery etc, then I dare say you would do more modifications anyway, which would necessitate the custom tuning and pc3.

**boomer** · 24th November 2007, 02:53

Originally Posted by Gremlin

re the 10, the slip on and cat isn't a big difference really, from stock. Just depends why you are removing it, do you want to gain, or just make it sound better etc. Generally, on the 10, you just disable the cat, rather than remove, as the kawasaki bastards made it part of the headers. At least the cat motor doesn't have a load sensor like the gixxer.... now THAT really does you!

If you're wanting to gain power, improve delivery etc, then I dare say you would do more modifications anyway, which would necessitate the custom tuning and pc3.

what drugs are you on..? the cat was separate on the gixxer and the air sensor fits straight into the aftermarket pipe..There are no other sensors to worry about

ps.. get it tuned.

**Gremlin** · 24th November 2007, 19:13

Originally Posted by boomer

what drugs are you on..? the cat was separate on the gixxer and the air sensor fits straight into the aftermarket pipe..There are no other sensors to worry about

k7 must differ from the k5/6 then... if you tried to disconnect the cables from it (like on the 04/05 10) you got an FI error... which you had to bypass, as it had a load sensor or something (so could detect it wasn't pulling cables)

**boomer** · 24th November 2007, 19:27

Originally Posted by Gremlin

k7 must differ from the k5/6 then... if you tried to disconnect the cables from it (like on the 04/05 10) you got an FI error... which you had to bypass, as it had a load sensor or something (so could detect it wasn't pulling cables)

the k5/6 didnt have a cat :P

**Gremlin** · 24th November 2007, 19:59

Originally Posted by boomer

the k5/6 didnt have a cat :P

fine... exhaust valve... I dunno... woteva... its a stupid suzuki

**NinjaBoy** · 10th December 2007, 22:46

Originally Posted by NinjaBoy

So its booked in for a Dyno session in couple of weeks. See what happens then.

Just a quick update after getting it off the Dyno last week and testing at Puke over the weekend.

Well it came off the Dyno with a couple of horsie's less than my mate's Gixxer... same Dyno and year/model bike. But what's a couple between mates !?

First test day was on a hot/dry track so I could really give a good go. The main things I noticed were even smoother acceleration and noticeably more torque/grunt in the lower gears/revs. I might have been imaging it but the engine seemed more balanced as I blipped on downshifts...eg. I was able to snick it into first coming into the hairpin without the usual lurch from heavy engine braking. No backfiring that I noticed but Puke isn't a track where you shut down the throttle much.

Second day was a race day and a wet one at that. Both races were wet-ish. Smoothness on the throttle and linear power curve helped a lot with keeping traction. It definitely was a lot less peaky compared to the previous map, esp when getting back on the throttle.

Overall assessment it was worth the effort/expense to get a more predictable throttle response. I don't think its made much difference to overall horsepower but the better torque down low seems to accelerate there faster.

**Mental Trousers** · 11th December 2007, 09:19

Originally Posted by Gremlin

fine... exhaust valve... I dunno... woteva... its a stupid suzuki

He's got you there boomer

**Paulus** · 11th December 2007, 21:11

Thanks guys. R1 came with a pair of Arrow cans and Y pipe (which eliminates the cat) already fitted by previous owner (Qkchk). The R1 cat is right next to the shock so removal is generally regarded as a good thing to stop the shock from being overheated (I've been reading up on the R1 forum). The Arrows sound truely beautiful BTW and have plug in inserts to quieten them down when WOF time comes around.

I found the stock 04 R1 fuelling map (probably same as 06) on the net and it has a farily lean spot at 3000rpm and another (less lean) peaking at 8000rpm. Otherwise it is pretty rich which would tend to agree with the soot being deposited in the end cans. To be honest it seems to fuel about as well (or is that as badly???) as a stock one (seat of pants impression on another friends 06 R1) so I guess it seems okay.

The ZX-10R (04) is a friends bike with a shiny new Akrapovic carbon can on it. He is going to get it run up on a dyno with an exhaust analyzer. His seems a fair bit leaner and pops a lot on deceleration. I'll post up his findings when he gets them.